Because the victims are nearly all carp, the cause is unlikely to be water that is too warm or insufficient oxygen, he said. Carp are one of the more resilient fish and would not normally be the first to die under those conditions, McClymont said. He said there are diseases that are specific to carp.

The curious event drew Ukiah siblings Eleni, Paola and Chris Rodriguez to the lake on Tuesday. Their mother had told them about the dead fish the day before.

"We didn't believe her," said Paola Rodriguez, 17.

Eleni Rodriguez, 19, said she was worried someone had poisoned the fish.

"It's scary to see all those dead fishes," said Paola Rodriguez.

McClymont said more should be known about the fish deaths later this week.